Semiconductor chips which have integrated circuit arrangements and which contain security-relevant information, in particular semiconductor chips with an integrated circuit provided for smart cards, require the provision of protective measures which prevent the contents of the integrated circuit from being spied out. Conventional housings or coverings for semiconductor chips do not afford sufficient protection if the housings can be removed or a protective covering can be ground or etched away.
Security-relevant data, such as access codes, passwords or personal details, are often stored in the integrated circuit arrangements. Therefore, there is major interest in keeping this information secret. Algorithms which are to be kept secret and are integrated in the circuit arrangements, by way of example, in the event that they are disclosed by being read by means of optical and/or electron-optical examination techniques, bring about an immense economic loss to the manufacturer company or the user company. For providing protection against such analysis, there are a multiplicity of methods in which the surface of integrated circuits is covered so that the circuits cannot readily be analyzed.
Protective measures in the form of coverings can be circumvented, however, by stripping the coverings by etching away or by grinding and eroding subsequent layers, layer by layer. In the process, each newly emerging layer is acquired photographically or in some other way, so that a reliable picture of the overall construction of the semiconductor chip is obtained.
When grinding away a covering of a circuit arrangement formed on a substrate, where the substrate has a nonplanar, for example spherical, form, an analyzable surface cannot be removed layer by layer by the grinding method. Chemical separation of the covering by means of a solvent, an etchant or the like is still possible, however.